System and method for transmitting data in a video signal by modulating a video signal brightness level

ABSTRACT

A system and method is provided for transmitting data in a video signal by modulating a brightness level of the video signal. The invention comprises a video display unit that is capable of encoding data into a brightness level of a video signal and creating brightness modulated video images for display on a display screen. The invention also comprises a brightness modulated data receiver unit that is capable of receiving the brightness modulated video images from the display screen and decoding the data that is encoded in the brightness modulated video images. The modulation of the brightness level of the video signal is adjusted so that changes in the brightness level of the video signal are not perceptible to human vision.

The present invention is directed, in general, to audio-visual systemsand, more specifically, to a system and method for transmitting data ina video signal by modulating a brightness level of the video signal.

Video displays have traditionally been used to display video images andtext. Video displays such as liquid crystal display (LCD) monitors andtelevisions typically comprise a light source, one or more active matrixpanels, and a display screen. Light that is generated in the lightsource is modulated by the active matrix panels. An electronic circuitcontrols the pixels in the active matrix panels to modulate the lightthat is output by the light source. The resulting video image isdisplayed on the display screen. Display controls that are associatedwith the display screen allow a user to manually adjust several of thedisplay parameters that affect the image. One of the display parametersthat may be manually adjusted by a user is the brightness level of thedisplayed image.

There is a need in the art for a system and method that is capable oftransmitting data in a video signal by modulating a display parameter ofa video signal. In particular, there is a need in the art for a systemand method that is capable of transmitting data in a video signal bymodulating a brightness level of the video signal.

The system and method of the present invention is capable oftransmitting data in a video signal by modulating a brightness level ofthe video signal. Modulating the brightness level of the video signalenables the transmission of data in addition to the data that istransmitted in the audio portions and the video portions of the videosignal.

The brightness level modulation is performed at a high frequency so thatthe changes in the brightness level are imperceptible to human vision.The human eye integrates the brightness levels of a video display.Therefore the viewer will perceive only the average brightness of themodulated brightness levels. However, high frequency transitions betweenhigh brightness levels and low brightness levels can be detected by anoptical receiver.

A video display unit of the present invention encodes an input datastream in a video signal by adjusting the brightness levels of the videosignal. The resulting brightness modulated video images are displayed ona display screen. An optical receiver in a brightness modulated datareceiver unit detects the changes in the brightness level of the videosignal and outputs a signal that represents the brightness modulateddata. The brightness modulated data is processed in a brightnessmodulated data processor unit to recreate the original data stream thatwas encoded in the video signal. The data stream that is encoded in thevideo signal may be a data stream that represents an audio output, atext output, or a video output.

The video display unit of the invention comprises a brightness levelmodulating panel that is capable of receiving a data stream andmodulating a brightness level of a video signal to encode the datastream into the brightness level of the video signal. The brightnesslevel modulating panel modulates the brightness level of the videosignal during a data transmission period between two row refreshingperiods of the video signal.

The brightness level modulating panel is capable of encoding one type ofdata bit (e.g., bit “0”) during a data transmission period by settingthe brightness level of the video signal to a maximum level during afirst portion of the data transmission period and by setting thebrightness level of the video signal to a minimum level during a secondportion of the data transmission period. By setting the brightness levelof the video signal to a minimum level during the first portion of thedata transmission period and by setting the brightness level of thevideo signal to a maximum level during a second portion of the datatransmission period, the brightness level modulating panel is capable ofencoding one other type of data bit (e.g., bit “1”).

It is an object of the present invention to provide a system and methodfor transmitting data in a video signal by modulating a brightness levelof the video signal.

It is another object of the present invention to provide a system andmethod for transmitting data in a video signal by modulating abrightness level of the video signal during a data transmission periodbetween two row refreshing periods of the video signal.

It is also an object of the present invention to provide a video displayunit that is capable of encoding a data stream into a brightness levelof a video signal to create brightness modulated data images for displaythat contain the encoded data stream within the brightness level of thevideo signal.

It is another object of the present invention to provide a brightnessmodulated data receiver unit that is capable of receiving the brightnessmodulated data images that are created by the video display unit anddecoding the data stream that is encoded within the brightness modulateddata images.

It is also an object of the present invention to provide a system andmethod for transmitting data in a video signal by modulating abrightness level of the video signal in a manner that causes themodulation of the brightness level of the video signal to beimperceptible to human vision.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention so that those skilled in the art maybetter understand the detailed description of the invention thatfollows. Additional features and advantages of the invention will bedescribed hereinafter that form the subject of the claims of theinvention. Those skilled in the art should appreciate that they mayreadily use the conception and the specific embodiment disclosed as abasis for modifying or designing other structures for carrying out thesame purposes of the present invention. Those skilled in the art shouldalso realize that such equivalent constructions do not depart from thespirit and scope of the invention in its broadest form.

Before undertaking the Detailed Description of the Invention, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document: the terms “include” and “comprise” andderivatives thereof, mean inclusion without limitation; the term “or,”is inclusive, meaning and/or; the phrases “associated with” and“associated therewith,” as well as derivatives thereof, may mean toinclude, be included within, interconnect with, contain, be containedwithin, connect to or with, couple to or with, be communicable with,cooperate with, interleave, juxtapose, be proximate to, be bound to orwith, have, have a property of, or the like; and the term “controller,”“processor,” or “apparatus” means any device, system or part thereofthat controls at least one operation, such a device may be implementedin hardware, firmware or software, or some combination of at least twoof the same. It should be noted that the functionality associated withany particular controller may be centralized or distributed, whetherlocally or remotely. In particular, a controller may comprise one ormore data processors, and associated input/output devices and memory,that execute one or more application programs and/or an operating systemprogram. Definitions for certain words and phrases are providedthroughout this patent document. Those of ordinary skill in the artshould understand that in many, if not most instances, such definitionsapply to prior uses, as well as future uses, of such defined words andphrases.

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, wherein likenumbers designate like objects, and in which:

FIG. 1 is a block diagram that illustrates an advantageous embodiment ofa video display unit and a brightness level modulating panel inaccordance with the principles of the present invention;

FIG. 2 is a block diagram that illustrates an advantageous embodiment ofa brightness modulated data receiver unit and an optical receiver inaccordance with the principles of the present invention;

FIG. 3(a) is a diagram that illustrates an exemplary brightness level ofa video signal in accordance with an advantageous embodiment of abi-phase amplitude modulation method of the invention;

FIG. 3(b) is a diagram that illustrates an exemplary data sync signal inaccordance with an advantageous embodiment of a bi-phase amplitudemodulation method of the invention;

FIG. 3(c) is a diagram that illustrates an exemplary horizontal syncsignal in accordance with an advantageous embodiment of a bi-phaseamplitude modulation method of the invention;

FIG. 4(a) is a diagram that illustrates a first exemplary brightnesslevel of a video signal in accordance with an advantageous embodiment ofan asymmetric bi-phase amplitude modulation method of the presentinvention;

FIG. 4(b) is a diagram that illustrates a second exemplary brightnesslevel of a video signal in accordance with an advantageous embodiment ofan asymmetric bi-phase amplitude modulation method of the presentinvention;

FIG. 4(c) is a diagram that illustrates a third exemplary brightnesslevel of a video signal in accordance with an advantageous embodiment ofan asymmetric bi-phase amplitude modulation method of the presentinvention;

FIG. 5 illustrates a flowchart showing the steps of an advantageousembodiment of a first portion of the method of the invention;

FIG. 6 illustrates a flowchart showing the steps of an advantageousembodiment of a second portion of the method of the invention;

FIG. 7 is a diagram that illustrates the use of the present invention ina headset that provides a plurality of audio programs in differentforeign languages; and

FIG. 8 is a diagram that illustrates the use of the present invention ina headset that provides an audio program for a video program that isdisplayed without an audio program.

FIGS. 1 through 8, discussed below, and the various embodiments used todescribe the principles of the present invention in this patent documentare by way of illustration only and should not be construed in any wayto limit the scope of the invention. The present invention may be usedin any suitable audio-visual system.

FIG. 1 is a block diagram that illustrates an advantageous embodiment ofa video display unit 100 and a brightness level modulating panel 120 inaccordance with the principles of the present invention. Video displayunit 100 receives video signals from a video signal source 110. Thevideo signals from video signal source 110 are provided as a first inputto brightness level modulating panel 120. Video display unit 100 alsocomprises a light source 150 and a light source driver 160. Light source150 may comprise, for example, light emitting diodes (LEDs). Lightsource driver 160 may comprise, for example, a light emitting diode(LED) driver. The output of light source 150 is provided as a secondinput to brightness level modulation panel 120.

A data stream from data source 170 (designated DATA INPUT) is providedto light source driver 160. Light source driver 160 modulates lightsource 150 in accordance with the data stream from data source 170.Brightness level modulating panel 120 then modulates the brightnesslevel of the video signal from video signal source 110 to encode thedata stream from data source 170. The brightness modulated video imagesare then output to display screen 130 and the video images are presentedfor viewing. Display screen 130 may comprise any conventional type ofdisplay screen (e.g., television, computer monitor, flat panel displayscreen).

Brightness level modulating panel 120 provides a data synchronizationsignal (designated DATA SYNC) to light source driver 160. In addition, ascreen control unit 140 coupled to display screen 130 provides a manualbrightness control signal (designated MANUAL BRIGHTNESS CONTROL) tolight source driver 160. If a viewer of display screen 130 manuallychanges the brightness level of the images displayed on display screen130, then the change in brightness level will be communicated to lightsource driver 160. Light source driver 160 will then adjust thebrightness level of light source 150 accordingly.

FIG. 2 is a block diagram that illustrates an advantageous embodiment ofa brightness modulated data receiver unit 210 and an optical receiver220 in accordance with the principles of the present invention.Brightness modulated video images 200 from display screen 130 areincident on optical receiver 220. As previously mentioned, opticalreceiver 220 detects the changes in the brightness level of the videosignal in the brightness modulated video images 200. Optical receiver220 outputs a signal that represents the brightness modulated data tobrightness modulated data processor unit 230. Brightness modulated dataprocessor unit 230 processes the brightness modulated data to re-createthe original data stream from data source 170 that was encoded in thevideo signal by brightness level modulating panel 120.

Brightness modulated data processor unit 230 decodes audio data from thebrightness modulated data and provides the audio data to audio outputunit 240. Alternatively, brightness modulated data processor unit 230decodes text data from the brightness modulated data and provides thetext data to text output unit 250. Alternatively, brightness modulateddata processor unit 230 decodes video data from the brightness modulateddata and provides the video data to video output unit 260.

FIGS. 3(a)-3(c) are diagrams that illustrates an exemplary brightnesslevel 310 of a video signal, a data sync signal 340 and a horizontalsync signal 350 (designated H SYNC 350) in accordance with anadvantageous embodiment of the invention. The magnitude of brightnesslevel 310 and the magnitude of data sync signal 340 and the magnitude ofhorizontal sync signal 350 are shown as a function of time.

As shown in FIGS. 3(a)-3(c), data transmission periods of the presentinvention are located in between row refreshing periods. In prior artsystems no data is transmitted during the time between the rowrefreshing periods. During a row refreshing period the pixels in thedisplay that correspond to an entire row are refreshed. In the presentinvention exemplary data transmission period 320 and exemplary datatransmission period 330 are located between row refreshing periods.Modulating the brightness level 310 during the data transmissionperiods(320, 330) enablesoneormore bits to be transmitted.

FIG. 3(a) illustrates an advantageous embodiment of a method of theinvention in which one (1) bit is transmitted during each datatransmission period. In the advantageous embodiment shown in FIG. 3(a),during data transmission period 320 a signal that represents a bit “0”is transmitted. The bit “0” signal comprises a first one half of thetransmission period 320 in which the brightness level 310 is at amaximum allowable level (designated MAX) and a second one half of thetransmission period 320 in which the brightness level 310 is at aminimum allowable level (designated MIN). After the data transmissionperiod 320 has ended, the brightness level returns to the brightnesslevel that existed before the beginning of data transmission period 320.

In the advantageous embodiment shown in FIG. 3(a), during datatransmission period 330 a signal that represents a bit “1” istransmitted. The bit “1” signal comprises a first one half of thetransmission period 330 in which the brightness level 310 is at aminimum allowable level (designated MIN) and a second one half of thetransmission period 330 in which the brightness level 310 is at amaximum allowable level (designated MAX). After the data transmissionperiod 330 has ended, the brightness level returns to the brightnesslevel that existed before the beginning of data transmission period 330.

In the example shown in FIG. 3(a), the representation of a bit “0”corresponds to a “high-to-low” transition from the maximum value ofbrightness to the minimum value of brightness. The representation of abit “1” corresponds to a “low-to-high” transition from the minimum valueof brightness to the maximum value of brightness. The transitionsbetween the maximum and minimum brightness levels facilitate thedetection of the transitions by optical receiver 220. The datasynchronization signal 340 signals the beginning of each datatransmission period. Similarly, the horizontal synchronization signal350 signals the beginning of each row refreshing period.

It is understood that the modulation patterns for bit “0” and for bit“1” shown in FIG. 3(a) are merely examples. Other types of modulationpatterns might be employed to represent bit “0” and to represent bit “1”during the data transmission periods (320, 330). In addition, it isunderstood that the example of transmitting one bit per datatransmission period is also merely an example. In alternate embodimentsof the present invention, more than one bit may be transmitted during adata transmission period.

There should be no perceptible brightness variation for a human viewerfor any brightness modulated data pattern. This requires that theaverage value of the modulated brightness data pattern during thetransmission of a bit “0” data bit be equal to the average value of themodulated brightness data pattern during the transmission of a bit “1”data bit. Arranging the brightness modulated data patterns so that theaverage value of the modulated brightness data pattern is the same foreach bit that is transmitted may be referred to as “bi-phase amplitudemodulation.”

FIGS. 4(a)-4(c) are diagrams that illustrate three exemplary brightnesslevels (410, 440, 470) of a video signal in accordance with anadvantageous embodiment of an asymmetric bi-phase amplitude modulationmethod of the present invention. In FIG. 4(a) the brightness level 410during a row refreshing period has a high value. That is, the brightnesslevel 410 is relatively near the maximum allowable level MAX. In orderto maintain an average value of the modulated brightness data patternduring data transmission period 420 that is approximately equal to thebrightness level 410 during a row refreshing period, a first portion ofthe data transmission period 420 (in which the brightness level 410 isat a maximum allowable level MAX) is longer in duration than a secondportion of the data transmission period 420 (in which the brightnesslevel 410 is at a minimum allowable level MIN).

Similarly, in order to maintain an average value of the modulatedbrightness data pattern during data transmission period 430 that isapproximately equal to the brightness level 410 during a row refreshingperiod, a first portion of the data transmission period 430 (in whichthe brightness level 410 is at a minimum allowable level MIN) is shorterin duration than a second portion of the data transmission period 430(in which the brightness level 410 is at a maximum allowable level MIN).

The length of time of a first portion of a data transmission period andthe length of time of a second portion of the data transmission periodare adjusted so that the average value of the modulated brightness datapattern during the data transmission period is approximately equal tothe value of the brightness level during a row refreshing period.Adjusting the relative lengths of the first and second portions of abrightness modulated data pattern so that the average value of themodulated brightness data pattern during the data transmission period isapproximately equal to the value of the brightness level during a rowrefreshing period may be referred to as “asymmetric bi-phase amplitudemodulation.”

Asymmetric bi-phase amplitude modulation may be used to minimize anyreduction in the maximum display brightness that may be caused bybrightness level modulation during the data transmission periods.Asymmetric bi-phase amplitude modulation may also be used to minimizeany increase in the minimum display brightness that may be caused bybrightness level modulation during the data transmission periods

In FIG. 4(b) the brightness level 440 during a row refreshing period hasa medium value. That is, the brightness level 440 is approximatelyhalfway between the minimum allowable level MIN and the maximumallowable level MAX. In order to maintain an average value of themodulated brightness data pattern during data transmission period 450that is approximately equal to the brightness level 440 during a rowrefreshing period, a first portion of the data transmission period 450(in which the brightness level 440 is at a maximum allowable level MAX)is approximately equal in duration to a second portion of the datatransmission period 450 (in which the brightness level 440 is at aminimum allowable level MIN).

Similarly, in order to maintain an average value of the modulatedbrightness data pattern during data transmission period 460 that isapproximately equal to the brightness level 440 during a row refreshingperiod, a first portion of the data transmission period 460 (in whichthe brightness level 440 is at a minimum allowable level MIN) isapproximately equal in duration to a second portion of the datatransmission period 460 (in which the brightness level 440 is at amaximum allowable level MIN).

In FIG. 4(c) the brightness level 470 during a row refreshing period hasa low value. That is, the brightness level 470 is relatively near theminimum allowable level MIN. In order to maintain an average value ofthe modulated brightness data pattern during data transmission period480 that is approximately equal to the brightness level 470 during a rowrefreshing period, a first portion of the data transmission period 480(in which the brightness level 470 is at a maximum allowable level MAX)is shorter in duration than a second portion of the data transmissionperiod 480 (in which the brightness level 470 is at a minimum allowablelevel MIN).

Similarly, in order to maintain an average value of the modulatedbrightness data pattern during data transmission period 490 that isapproximately equal to the brightness level 470 during a row refreshingperiod, a first portion of the data transmission period 490 (in whichthe brightness level 470 is at a minimum allowable level MIN) is longerin duration than a second portion of the data transmission period 490(in which the brightness level 470 is at a maximum allowable level MIN).

FIG. 5 illustrates a flowchart showing the steps of an advantageousembodiment of a first portion of the method of the invention. The stepsof the method shown in FIG. 5 are collectively referred to withreference numeral 500. In the first step shown in FIG. 5, data source170 provides a data stream to light source driver 160 of video displayunit 100 (step 510). Then light source driver 160 modulates light source150 of video display unit 100 with the data stream from data source 170(step 520). Brightness level modulating panel 530 modulates thebrightness level of a video signal from video signal source 110 in orderto encode the data stream from data source 170 (step 530). Thebrightness modulated video images from brightness level modulating panel120 contain the encoded data stream from data source 170. Brightnesslevel modulating panel 120 then provides the brightness modulated videoimages to display screen 130 (step 540). Optical reader 220 inbrightness modulated data receiver unit 210 reads the brightnessmodulated data from the display screen 130 and brightness modulated dataprocessor unit 230 recreates the original data stream from data source170 (step 550).

FIG. 6 illustrates a flowchart showing the steps of an advantageousembodiment of a second portion of the method of the invention. The stepsof the method shown in FIG. 6 are collectively referred to withreference numeral 600. In the first step shown in FIG. 6, brightnesslevel modulating panel 120 receives a brightness level 310 of a videosignal (step 610). Brightness level modulating panel 120 also receives adata bit to be modulated within brightness level 310 (step 620).Brightness level modulating panel 120 modulates brightness level 310during a data transmission period between two row refreshing periods(step 630). Brightness level modulating panel 120 determines whether thedata bit to be encoded is a bit “0” data bit (decision step 640).

If the data bit to be encoded is a bit “0” data bit, then brightnesslevel modulating panel 120 sets the brightness level 310 to the maximumlevel MAX for the first half of data transmission period and to theminimum level MIN for the second half of the data transmission period(step 650). Then brightness level modulating panel 120 sets thebrightness level 310 to its previous brightness level after the datatransmission period ends (step 670).

If the data bit to be encoded is not a bit “0” data bit, then it is abit “1” data bit. In that case, brightness level modulating panel 120sets the brightness level 310 to the minimum level MIN for the firsthalf of data transmission period and to the maximum level MAX for thesecond half of the data transmission period (step 660). Then brightnesslevel modulating panel 120 sets the brightness level 310 to its previousbrightness level after the data transmission period ends (step 670).

The system and method of the present invention may be used in numerousapplications. For example, FIG. 7 illustrates an advantageousapplication in which the invention is capable of receiving and playingaudio signals that represent different languages. Display screen 130displays a video program in which the audio portion is in English. Audiodata streams that represent an audio portion in German, and audioportion in French, and an audio portion in Spanish have been encoded inthe brightness modulated video images 200. Brightness modulated datareceiver 210 of the present invention may be associated with a headset710 to receive and decode the brightness modulated audio data streams inthe brightness modulated video images 200. Optical reader 220 (not shownin FIG. 7) reads the encoded audio data streams and brightness modulateddata processor unit 230 (not shown in FIG. 7) decodes the encoded audiodata streams to recover the foreign language audio portions.

Brightness modulated data receiver unit 210 in headset 710 provides theGerman audio signal 720, and the French audio signal 730, and theSpanish audio signal 740 to earphones 750. The user selects the desiredaudio signal using audio version switch 760. This advantageousembodiment of the present invention may be used in any type ofaudio-visual presentation in which the audience is made up of personswho do not speak the same language.

FIG. 8 illustrates an advantageous application in which the invention iscapable of receiving and playing an audio program for a video programthat is displayed without an audio program. This type of display mayoccur during the presentation of movies during an airplane flight. Inthe prior art, it is necessary for the user to plug a headset into anaudio outlet plug near the user in order to head the audio program thatrelates to the video program. The present invention does not need toemploy an audio outlet plug. The present invention is capable ofobtaining the audio program from brightness modulated video images.

Display screen 130 displays a video program in which the correspondingaudio program is not audibly transmitted. An audio data stream thatrepresents the corresponding audio program has been encoded in thebrightness modulated video images 200. Brightness modulated datareceiver 210 of the present invention may be associated with a headset810 to receive and decode the brightness modulated audio data stream inthe brightness modulated video images 200. Optical reader 220 (not shownin FIG. 8) reads the encoded audio data streams and brightness modulateddata processor unit 230 (not shown in FIG. 8) decodes the encoded audiodata stream to recover the corresponding audio program.

Brightness modulated data receiver unit 210 in headset 810 provides theaudio program signal 820 to earphones 830 for the user. Thisadvantageous embodiment of the present invention may be used in any typeof audio-visual presentation in which an audio program is not presentedwith its corresponding video program.

While the present invention has been described in detail with respect tocertain embodiments thereof, those skilled in the art should understandthat they can make various changes, substitutions modifications,alterations, and adaptations in the present invention without departingfrom the concept and scope of the invention in its broadest form.

1. An apparatus (100,210) that transmits data (320,330) in a videosignal by modulating a brightness level (310) of said video signal. 2.An apparatus (100,210) as claimed in claim 1 wherein said apparatusmodulates said brightness level (310) of said video signal during a datatransmission period between two row refreshing periods of said videosignal.
 3. An apparatus (100,210) as claimed in claim 1 wherein saidapparatus comprises: a video display unit that is capable of encodingsaid data (320,330) into said brightness level (310) of said videosignal to create brightness modulated video images (200); and abrightness modulated data receiver unit (210) that is capable ofreceiving said brightness modulated video images (200) and decoding saiddata (320,330) from said brightness modulated video images (200).
 4. Anapparatus (100,210) as claimed in claim 3 wherein said video displayunit comprises a brightness level modulating panel (120) that is capableof modulating said brightness level (310) of said video signal to encodesaid data (320,330) into said brightness level (310) of said videosignal.
 5. An apparatus (100,210) as claimed in claim 3 wherein saidbrightness modulated data receiver unit (210) comprises: an opticalreceiver (220) that is capable of receiving said brightness modulatedvideo images (200) from said video display unit (100) and detectingchanges in said brightness level (310) of said video signal thatrepresent said data (320,330) that is encoded into said brightness level(310) of said video signal; and a brightness modulated data processorunit (230) that is capable of decoding said data (320,330) from saidbrightness modulated video images that are detected by said opticalreceiver (220).
 6. An apparatus (100,210) as claimed in claim 5 whereinsaid brightness modulated data processor unit (230) decodes said data(320,330) from said brightness modulated video images (200) to recreateone of: an audio output, a text output, and a video output.
 7. Anapparatus (100,210) as claimed in claim 3 wherein said brightness levelmodulating panel (120) modulates said brightness level (310) of saidvideo signal to encode at least one bit (320) of said data (320,330)into said brightness level (310) of said video signal in a datatransmission period between two row refreshing periods of said videosignal.
 8. An apparatus (100,210) as claimed in claim 7 wherein saidbrightness level modulating panel (120) modulates said brightness level(310) of said video signal using one of: bi-phase amplitude modulationand asymmetric bi-phase amplitude modulation.
 9. An apparatus (100,210)as claimed in claim 3 wherein said data that said video display unit(100) encodes into said brightness level (310) of said video signal tocreate brightness modulated video images (200) comprises at least oneforeign language audio program; and wherein said data that saidbrightness modulated data receiver unit (210) receives and decodes fromsaid brightness modulated video images (200) comprises said at least oneforeign language audio program.
 10. An apparatus (100,210) as claimed inclaim 3 wherein said data that said video display unit (100) encodesinto said brightness level (310) of said video signal to createbrightness modulated video images (200) comprises an audio program for avideo program for which said audio program is not audibly transmitted;and wherein said data that said brightness modulated data receiver unit(210) receives and decodes from said brightness modulated video images(200) comprises said audio program for said video program for which saidaudio program is not audibly transmitted.
 11. A method for transmittingdata (320,330) in a video signal, said method comprising the step ofmodulating a brightness level (310) of said video signal.
 12. The methodas claimed in claim 11 further comprising the step of: modulating saidbrightness level (310) of said video signal during a data transmissionperiod between two row refreshing periods of said video signal.
 13. Themethod as claimed in claim 11 further comprising the steps of: encodingsaid data (320,330) into said brightness level (310) of said videosignal in a video display unit (100) to create brightness modulatedvideo images (200); receiving said brightness modulated video images(200) in a brightness modulated data receiver unit (210); and decodingsaid data (320,330) from said brightness modulated video images (200).14. The method as claimed in claim 13 further comprising the step of:modulating said brightness level (310) of said video signal in abrightness level modulating panel (120) of said video display unit (100)to encode said data (320,330) into said brightness level (310) of saidvideo signal.
 15. The method as claimed in claim 13 further comprisingthe steps of: receiving said brightness modulated video images (200)from said video display unit (100) in an optical receiver (220);detecting in said optical receiver (220) changes in said brightnesslevel (310) of said video signal that represent said data (320,330) thatis encoded into said brightness level (310) of said video signal; anddecoding in a brightness modulated data processor unit (230) said datafrom said brightness modulated video images (200) that are detected bysaid optical receiver (220).
 16. The method as claimed in claim 15further comprising the step of: decoding said data (320,330) from saidbrightness modulated video images (200) to recreate one of: an audiooutput, a text output, and a video output.
 17. The method as claimed inclaim 13 further comprising the step of: modulating said brightnesslevel (310) of said video signal to encode at least one bit (320) ofsaid data (320,330) into said brightness level (310) of said videosignal in a data transmission period between two row refreshing periodsof said video signal.
 18. The method as claimed in claim 17 furthercomprising the step of: modulating said brightness level (310) of saidvideo signal using one of: bi-phase amplitude modulation and asymmetricbi-phase amplitude modulation.
 19. The method as claimed in claim 13further comprising the steps of: encoding data (320,330) that comprisesat least one foreign language audio program into said brightness level(310) of said video signal to create brightness modulated video images(200); receiving said brightness modulated video images (200); anddecoding from said brightness modulated video images (200) said datathat comprises said at least one foreign language audio program.
 20. Themethod as claimed in claim 13 further comprising the steps of: encodingdata (320,330) that comprises an audio program for a video program forwhich said audio program is not audibly transmitted into said brightnesslevel (310) of said video signal to create brightness modulated videoimages (200); receiving said brightness modulated video images (200);and decoding from said brightness modulated video images (200) said data(320,330) that comprises said audio program for said video program forwhich said audio program is not audibly transmitted.
 21. An encodedvideo signal (310) generated by a method for transmitting data (320,330)in a video signal, said method comprising the step of modulating abrightness level (310) of said video signal.
 22. An encoded video signal(310) as claimed in claim 21 wherein said method further comprises thestep of: modulating said brightness level (310) of said video signalduring a data transmission period between two row refreshing periods ofsaid video signal.
 23. An encoded video signal (310) as claimed in claim21 wherein said method further comprises the steps of: encoding saiddata (320,330) into said brightness level (310) of said video signal ina video display unit (100) to create brightness modulated video images(200); receiving said brightness modulated video images (200) in abrightness modulated data receiver unit (210); and decoding said data(320,330) from said brightness modulated video images (200).
 24. Anencoded video signal (310) as claimed in claim 23 wherein said methodfurther comprises the step of: modulating said brightness level (310) ofsaid video signal in a brightness level modulating panel (120) of saidvideo display unit (100) to encode said data (320, 330) into saidbrightness level (310) of said video signal.
 25. An encoded video signal(310) as claimed in claim 23 wherein said method further comprises thesteps of: receiving said brightness modulated video images (200) fromsaid video display unit (100) in an optical receiver (220); detecting insaid optical receiver (220) changes in said brightness level (310) ofsaid video signal that represent said data 320,330) that is encoded intosaid brightness level (310) of said video signal; and decoding in abrightness modulated data processor unit (230) said data (320,330) fromsaid brightness modulated video images that are detected by said opticalreceiver.
 26. An encoded video signal as claimed in claim 25 whereinsaid method further comprises the step of: decoding said data from saidbrightness modulated video images to recreate one of: an audio output, atext output, and a video output.
 27. An encoded video signal as claimedin claim 23 wherein said method further comprises the step of:modulating said brightness level of said video signal to encode at leastone bit of said data into said brightness level of said video signal ina data transmission period between two row refreshing periods of saidvideo signal.
 28. An encoded video signal as claimed in claim 27 whereinsaid method further comprises the step of: modulating said brightnesslevel of said video signal using one of: bi-phase amplitude modulationand asymmetric bi-phase amplitude modulation.
 29. An encoded videosignal as claimed in claim 23 wherein said method further comprises thesteps of: encoding data that comprises at least one foreign languageaudio program into said brightness level of said video signal to createbrightness modulated video images; receiving said brightness modulatedvideo images; and decoding from said brightness modulated video imagessaid data that comprises said at least one foreign language audioprogram.
 30. An encoded video signal as claimed in claim 23 wherein saidmethod further comprises the steps of: encoding data that comprises anaudio program for a video program for which said audio program is notaudibly transmitted into said brightness level of said video signal tocreate brightness modulated video images; receiving said brightnessmodulated video images; and decoding from said brightness modulatedvideo images said data that comprises said audio program for said videoprogram for which said audio program is not audibly transmitted.